The present invention relates to a groove stamping machine for stamping stator plates, rotor plates, core plates and similar grooved metal plates for electric motors and transformers.
Several processes are known for producing grooved stator and rotor plates for electric machines as well as transformer plates. In these processes, an individual stator plate and rotor plate are obtained in steps by being stamped from a single sheet metal blank. During the implementation of this process, the individual grooves of the respective section of the blank which is part of the future stator or rotor plate are stamped successively.
A groove stamping machine, which is set up for such a manufacturing of stator and rotor plates, is described in DE-OS 29 19 687. This groove stamping machine has a stationarily disposed groove stamping device with exchangeable tools to which a spacing apparatus is assigned. The spacing apparatus is used for the holding of a workpiece to be machined which is formed by a disk-shaped blank (sheet metal blank). The disk-shaped blank is held by the spacing apparatus in a horizontal plane and is disposed to be rotatable about a vertical axis. The spacing apparatus adjusts the workpiece in steps about the vertical axis while the groove stamping press stamps a groove after each adjusting step. For an adaptation to different plate or workpiece diameters, the spacing apparatus is disposed to be adjustable away from and toward the groove stamping device.
When very small stator and rotor plates are to be stamped, the spacing apparatus must be moved very close to the groove stamping device. This may impair the access possibilities of an operator with respect to the workpiece.
DE 26 04 639 C2 describes a workpiece arrangement for producing grooved plate segments, and having a stationarily disposed groove stamping device with a stationary bench fastened thereto. A spacing apparatus for the holding and angular adjustment of the core plate to be stamped is disposed on the bench and can be adjusted toward and away from the groove stamping device. In this known arrangement which in principle corresponds to the above-described groove stamping machine, the bench extends relatively far away from the groove stamping device. The bench therefore makes the access to the workpiece more difficult.
Furthermore, it was found to be difficult in the case of groove stamping machines with an adjustable spacing apparatus to manufacture core plates with a fairly high precision. Groove stamping machines frequently operate with relatively high stamping frequencies. In this case, relatively high masses are considerably accelerated in a constantly repeated manner and are braked again. The high operating speed is required for achieving a high output also in the case of a serial, that is, successive stamping of individual grooves. A machining precision is desired which, in the individual case, may be in the micrometer range, in which case, if possible, the stator or rotor plates should be usable without any finishing. Also if possible, the machining precision should be ensured in a constant manner without any readjustment. Further, the groove stamping machine must be adaptable in a simple manner to different stator or rotor plate sizes and shapes.
It is an object of the present invention to provide a groove stamping machine which, in a simple manner, can be adapted to different stator and rotor plate sizes and in the process, permits a high production output as well as a good machining precision.
This object has been achieved in accordance with the present invention by the provision of a groove stamping machine having an oblong bench which can be arranged in a stationary manner and on whose one end a workpiece holding device is arranged on the top side, having clamping devices provided on the workpiece holding device for the chucking and positioning of workpieces, having a stamping device which is arranged to be longitudinally adjustable on the bench in a direction away from the workpiece holding device and toward the workpiece holding device and which can be equipped with a tool for machining the workpiece, having a low-friction, stiff bearing device which is arranged between the bench and the stamping device, having a transmission device for adjusting the distance between the workpiece holding device and the stamping device which with one end is supported on the workpiece holding device in the proximity of the clamping devices and with its other end is supported on the stamping device in the proximately of the tool.
The groove stamping machine has a bench on which a workpiece holding device, which is preferably constructed as a spacing apparatus, is disposed in a stationary manner. In contrast, the stamping device is disposed on the bench in an adjustable manner and can therefore be displaced toward the spacing apparatus and away therefrom. As the result of the adjustability of the distance between the spacing apparatus and the stamping device, workpieces with different diameters can be processed. In this event, the workpiece is always mounted on the stationarily disposed spacing apparatus at the same point so that stator or rotor plates with a small diameter are also easily accessible. During the cutting or stamping operation, the stamping device of the groove stamping machine is disposed in a floating manner.
For processing workpieces, the stamping press is moved closer to the spacing apparatus, while otherwise it is arranged to be farther away from the spacing apparatus which is formed by a supporting table provided with corresponding clamping devices and does not change its position during the adjustment of the workpiece size. The stamping device is supported on the bench by way of a low-friction and rigid bearing device. As a result of the low friction, particularly a low static friction, a very precise adjustment is permitted of the distance between the stamping device and the supporting table. This permits high processing precision on the workpiece, whereas the rigidity of the bearing device permits high operating speed of the stamping device which goes along with high mass accelerations, acceleration forces and resulting shock loads of the bearing device.
For adjusting the distance between the supporting table and the stamping device, a transmission device is arranged at a narrow distance to the workpiece between the stamping device and the supporting table. The transmission device determines the distance between the stamping device and the supporting table. Vibrations or other deformations of the bench, the supporting table and particularly of the stamping device do not substantially affect the adjusted distance. A warping or bending of the bench, for example, as the result of a heating of the bench on its top side when its bottom side remains cool, does not result in a corresponding change of the distance of the stamping device from the supporting table. On the contrary, the distance is determined by the transmission device. Other length changes caused by forces or the effect of heat are compensated by way of the bearing device and do not, or only very little, impair the precision during the manufacturing of the core plates.
The transmission device can be constructed as a threaded spindle, preferably a ball thread spindle. As a result of a mechanical prestressing, this spindle is constructed free of play and with little friction. The ball thread spindle is rotatably disposed, for example, on the workpiece holding device, and a ball circulating nut is connected with the stamping machine. The distance between the rotatable end-side bearing of the ball thread spindle and the nut defines the effective length of the transmission device or, more concretely, of the threaded spindle. When this effective length corresponds to the distance of the rotation axis of the spacing apparatus (or workpiece holding device) and the stamping tool stamping the grooves, the influences of temperature changes on the machining precision can be reduced. With the same temperature change of the workpiece and the spindle, their length changes are also approximately the same so that the stamping operation takes place with a good precision at the point provided for this purpose.
For the foregoing purpose, the transmission device, particularly the threaded spindle, can be advantageously arranged such that, during the operation of the stamping machine, it can essentially assume the ambient temperature. That is, the transmission device or the threaded spindle is arranged to be exposed to the ambient air. In addition, the transmission device can be insulated with respect to heat sources of the stamping machine. An insulation is achieved, for example, by the absence of a massive connection between heat sources and the ball circulating nut or a corresponding transmission element. It is assumed that, because of the storage, workpieces have an ambient temperature. When the ball thread spindle also assumes ambient temperature, the temperatures will be the same. Temperature changes within the course of a workday therefore impair the machining precision little or not at all because of the same-length changes.
When the threaded spindle is arranged with its longitudinal axis at a narrow distance from the workpiece to be machined, a particularly stiff coupling of the stamping device to the spacing apparatus is achieved. The distance between the two is largely unaffected by vibrations and deformations of the rest of the groove stamping machine.
Although it is basically possible to determine a distance adjusted by the threaded spindle or generally the transmission device by fixing the stamping device on the bench, the transmission device, i.e. particularly the ball thread spindle, is advantageously configured in a blockable manner. For this purpose, a controllable braking device can be used which affects the threaded spindle. Length changes or bending of the bench will then cause no change of the distance between the stamping device and the workpiece holding device or spacing apparatus.
This braking device should be dimensioned such that the threaded spindle is held in a non-rotatable manner when the braking device is operated. Shocks or vibrations occurring during the operation of the groove stamping device must be reliably absorbed without the occurrence of a rotation of the threaded spindle. The distance between the spacing apparatus and the groove stamping device, and thus the radius of the grooves to be stamped, is adjusted in a reliable and precise manner.
If a spring-loaded disk brake is used as the braking device, which preferably can be released electrically, a particularly stiff and precise blocking of the threaded spindle can be achieved. The operation of brake shoes, which are part of the disk brakes, takes place orthogonally with respect to the rotating direction so that an adjusted rotating position of the threaded spindle cannot be displaced or shifted by the operation of the brake shoes.
For the implementation of the rigid and low-friction bearing device, roller bearings with an additional stiffening were found to be particularly useful. The bearing device, which is preferably constructed as guide rollers, permits a low-friction and particularly almost static-friction-free displacement of the stamping device on the bench. For stiffening the bearing device, additional slide elements are provided which, when the stamping device is inoperative, are at a narrow distance from the corresponding slideways or rest against them without any contact pressure force. This slight play, which therefore usually exists between the slide elements and the slideways, has the result that almost no friction occurs during the displacement of the stamping device. Vibrations caused by the operation of the stamping device result in elastic deformations of the rollers or other rolling bodies. The slide elements are placed on the slideways and/or are pressed there against which, on the one hand, causes a stiff coupling of the stamping device to the bench and, on the other hand, relieves the rolling bodies. A destruction of the rolling bodies and a deformation of the roller paths is thereby prevented.